BACKGROUND AND OBJECTIVES: Painful polyneuropathy after chemotherapy
is often refractory to conservative clinical treatment. The objective of this
report was to demonstrate that spinal cord stimulation is an alternative to
conventional methods used in the treatment of patients with pain that is difficult
to control.CASE REPORT: A 72 year old patient with painful polyneuropathy after
chemotherapy approximately 10 years ago, presented severe, continuous, daily
pain (visual analog scale = 10) in the lower limbs despite the use of several
drugs specific for neuropathic pain. An epidural electrode was implanted, with
significant improvement in pain (visual analog scale = 3) and reduction in the
consumption of medication.CONCLUSION: Spinal cord stimulation constitutes a therapeutic option
in patients with peripheral neuropathy refractory to conventional clinical management
when properly indicated and within established criteria.

Electrical stimulation of the spinal cord has been used to
treat patients with different painful conditions, with varying
degrees of success 1. The first experiences of
Shealey, in 1967 and, later, Cook, in 1976, were done by
implanting spinal cord stimulation electrodes in patients with
incapacitating peripheral vasculopathies. There was an important
degree of pain control, as well as improvement in ischemic ulcer
cicatrisation 2.

The method is based on the gate theory of pain3, in which activation
of large diameter afferent fibers, A-b fibers, inhibits
painful transmission in small diameter fibers, fibers A-delta, to spinal neurons
that project to upper brain centers. Linderoth and Foreman proposed that the
antidromic activation of the posterior horn by stimulation of the spinal cord
could inhibit the hyperexcitability of neurons sensitized by a peripheral nerve
lesion. Besides, spinal and supraspinal structures could also be involved in
the analgesia obtained through stimulation of the spinal cord. Since the first
cases reported 30 years ago 6,7, the indications of spinal stimulation
have varied, used in different conditions such as post-laminectomy syndrome,
complex regional painful syndrome, postherpetic neuralgia, diabetic neuropathy,
ischemic pain secondary to vascular disease and angina 1,8,10. Implantation
of electrodes for spinal cord stimulation should be carefully done in selected
patients, whose conservative treatment has not been effective. There should
be a positive response, with a minimum of 50% relief in the severity of pain
during the trial period 1.

Electrical stimulation of the spinal cord is an
interventional technique to manage pain, which involves the
implantation of one or more electrodes in the epidural space,
their anchorage and positioning, initially for the test period
and, posteriorly, with tunnel formation and connection of the
electrodes to an implantable generator. Implantation of
electrodes in the epidural space for spinal cord stimulation
could be done through a laminectomy or percutaneous, through a
specific epidural needle. The technique of laminectomy is beyond
the scope of this paper. The percutaneous technique is the
preferred method for several reasons, such as: 1) it is less
aggressive and bloody; 2) does not require general anesthesia;
and 3) assures the proper positioning of the electrode, obtaining
adequate response of the stimulated area, since the patient
remains awake. In this technique, the electrode is positioned,
through a needle used to puncture the epidural space via the
paramedian approach. The electrode is introduced in the posterior
epidural space until the desired level guided by fluoroscopy. An
electrical stimulus is, then, delivered in an attempt to cover
the desired area with a paresthetic feeling induced by the
electrical stimulus. If the patient presents a good response in
the trial period, which might last from one to five days, the
definitive generator is implanted in the superior gluteal region,
where the patient can reach it with his/her dominant hand and,
therefore, adjust the parameters by means of a remote
control.

Painful peripheral neuropathy after chemotherapy is observed
in many patients treated with chemotherapeutic agents for
different types of malignant neoplasia, with varying frequency
and severity (depending on the drug used, duration of the
treatment, and the presence of comorbidities)
11-14.

Pain is the main complaint in those patients and, many times,
it has profound negative effects in the quality of life of
patients who have been cured or with increased survival
9. The main drugs involved in the genesis of
peripheral neuropathy include platinum compounds, alkaloids and
taxol. Patients affected by this type of neuropathy have been
treated with different types of medication including opioids,
anticonvulsants and antidepressants, often without demonstrating
satisfactory response. In the case presented here spinal cord
stimulation was an effective alternative in pain
control.

CASE REPORT

Male patient, 72 years old, retired, right-handed, had a past
medical history of renal cancer approximately 10 years before
this consultation. At that time, he was treated with nephrectomy
associated with adjuvant chemotherapy with vincristine.
Approximately 1 year before consultation, after the end of the
last course of chemotherapy, he developed pain, mainly in the
soles, bilaterally, gradually progressive, characterized by
stabbing pain and a burning sensation irradiating to the hips.
The patient sought several doctors in different subspecialties
from September 2004 on, when his symptoms started, without
improvement of the pain. In August 2005, he was referred to our
service. At that time, he complained of severe pain (visual
analog scale = 10), and had been medicated with 25 mg of
amitriptine a day, associated with codeine (90 mg/day), and
paracetamol (3 g/day).

A
therapeutic regimen with gradually increasing doses of
amitriptyline, gabapentin and tramadol up to 50 mg of
amitriptyline/day, 2400 mg of gabapentin/day and 400 mg of
tramadol/day was instituted. Eventually, increasing doses of
methadone, up to 30 mg/d, replaced the tramadol. At that time the
patient was also being followed by a psychologist and undergoing
physical therapy.

With this treatment, the patient referred only a 30%
improvement in pain (visual analog scale = 7). Due to the failure
in controlling his symptom pharmacologically and the development
of side effects, it was proposed to the patient a trial of spinal
cord stimulation, which was instituted after he signed an
informed consent.

A test of spinal
cord stimulation was scheduled for 5 months after institution of the new therapeutic
conservative regimen. Under sterile conditions, patient in ventral decubitus,
monitoring and venoclysis, 2 mg of midazolam and 20 µg of fentanyl were
administered. Oxygen (3 L.min-1) was administered by a nasal catheter.
After anesthetizing the area of the puncture with lidocaine without vasoconstrictor,
a paramedian puncture was performed at the level of L2, with a 16G
Tuohy needle (Figure 1). Proper positioning of the needle
in the epidural space was determined by the loss of resistance technique and
confirmed by fluoroscopy. An octopolar electrode was introduced in the posterior
epidural space and advanced up to the level of T10. After connecting
it to an external generator, an electrical stimulus was applied resulting in
paresthesia in most of the area affected by pain followed by significant analgesia
for 24 hours after beginning stimulation (visual analog scale = 3). After 72
hours, an implantable generator was connected to the octopolar electrode (Genesis,
ANS, Inc., plano, TX). The parameters of the generator that had the best results
were frequency of 80 hz, pulse amplitude of 300 µs, and voltage between
0 and 4V.

One month after implanting the electrode, the patient
referred relief of the pain (visual analog scale = 3), with an
important improvement in his quality of life, using the
stimulator approximately 18 hours a day and taking amitriptyline,
25 mg, and gabapentin, 900 mg/day. This improvement was
maintained three months after the procedure.

DISCUSSION

Post-chemotherapy neuropathy causing neuropathic pain is
common in patients treated for a wide scope of malignant
neoplasia. Usually, patients develop sensory symptoms, which can
start months or years after chemotherapy 15. It is
rarely associated with motor or autonomic dysfunction
18-20. Sensory symptoms are usually symmetrical and
described as dysesthetic paresthesias, electrical shocks, burning
or stabbing pain and often present in a "glove" or "boot"
distribution 19.

This case has two important aspects. First, the patient
referred an improvement in pain greater than 50% after spinal
cord stimulation, which was confirmed by other studies that
reported better evolution when a trial test is done before
implanting the definitive generator. Second and most important
aspect the reduction in the medication needed to control pain and
discontinuation of the opioid, with reduction in side effects.
The mechanisms responsible for those results are not known, but
several hypotheses have been postulated. The influence of the
spinal cord stimulation in the modulation of excitatory amino
acids in the spinal cord, dorsal root ganglion, activation of
supraspinal structures and their control over inhibitory
descending pathways are the mechanisms that might be affected by
the stimulation of the posterior horns of the spinal cord
3,21,22.

This report of a case of refractory, painful polyneuropathy, induced by chemotherapy
and treated with spinal cord stimulation shows that it can be an important alternative
for those patients. However, more studies are needed to validate this result.